Wide angle type cathode-ray tube

ABSTRACT

In a cathode-ray tube, the envelope comprises conical and neck portions wherein the conical portion has a rear cone section of rectangular truncated pyramidal shape and a front cone section flaring from the rear cone section at a wider angle.

United States Patent [191 Tsuneta et al.

[ WIDE ANGLE TYPE CATHODE-RAY TUBE [75] Inventors: Asahide Tsuneta,Kawasaki; Shinichi Sawagata, Tokyo, both of Japan [73] Assignee: TokyoShibaura Electric Co., Ltd.,

Kawasaki-shi, Japan 22 Filed: Feb. 22, 1972 211 Appl. No.: 228,191

Related U.S. Application Data [63] Continuation-impart of Ser. No.14,173, Feb. 25,

1970, abandoned.

[30] Foreign Application Priority Data Feb. 28, 1969 Japan 44-17635 Feb.28, 1969 Japan 44-17636 Feb. 28, 1969 Japan 44-17637 [52] U.S. Cl.313/64 [51] Int. Cl. H01j 29/00 [58] Field of Search 313/64 [56]References Cited UNITED STATES PATENTS 2,928,968 I 3/1960 Hoagland313/64 [451 Apr. 23, :1974

Tirico 313/76 2,591,521 4/1952 De Gier.... 313/64 2,767,342 10/1956Anthony 313/64 3,005,122 10/1961 Coleman et a1 313/64 3,564,329 2/1971Uetz 315/8 FOREIGN PATENTS OR APPLICATIONS 525,181 8/1940 Great Britain313/64 820,181 9/1959 Great Britain 313/64 867,824 9/1941 France 313/641,545,517 11/1968 France 313/64 Primary Examinerl-lerman Karl SaalbachAttorney, Agent, or FirmF1ynn & Frishauf [5 7] ABSTRACT ln a cathode-raytube, the envelope comprises conical and neck portions wherein theconical portion has a rear cone section of rectangular truncatedpyramidal shape and a front cone section flaring from the rear conesection at a wider angle.

6 Claims, 6 Drawing Figures PATENTEU APR 2 3 I974 FIG.2

FIG.4

CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part ofthe US. Patent Application Ser. No. 14,173, filed on Feb. 25, 1970, nowabandoned.

BACKGROUND OF THE INVENTION This invention relates to a cathode-ray tubeand more particularly to a wide angle type color cathode-ray tubeenvelope.

Due to the recent desire to have a television receiving set made morecompact and lighter, there has grown demand for a cathode-ray tubeenabling electron beams from an electron gun assembly to be deflected ata wider angle than has been possible in the past so as to provide acompact and light color television receiving set. To obtain acathode-ray tube permitting the wide deflection of electron beams, thereare raised problems in connection with the occurrence of the socalledneck shadows at the screen comers and requirement of larger amounts ofpower to deflect electron beams at a wider angle. The neck shadowsoriginate with the fact that electron beams deflected toward the screencorners are interrupted in their passage by the circular front edge ofthe cylindrical neck. To avoid the appearance of said neck shadows,electron beams have to be deflected at a limited angle, which in turnhas obstructed the development of a cathode-ray tube permitting thewider deflection of electron beams. Further, with the conventionalcathode-ray tube using a triple electron gun assembly, beams ofelectrons emitted from a particular member of said electron gun assemblyare liable to be interrupted in their passage at certain corners of theneck portion, obscuring or degrading the color image presented at thecorresponding screen corners. Moreover, the neck and conical portions ofthe prior art cathode-ray tube which are formed with a round crosssection present difficulties in properly locating a deflection coil.

As mentioned above, deflction of electron beams at a wider anglerequires larger amounts of deflection power, exerting a harmful effecton the other circuits of a television receiving set and furtherincreasing the power consumption of the receiving set as a whole. Acathode-ray tube of wide angle type used to date has a narrow neck toreduce required deflection power. However, such a narrow neck naturallydemands that an electron gun to be received therein be made fullynarrow, thus giving rise to a blooming effect.

SUMMARY OF THE INVENTION It is accordingly the object of this inventionto provide a cathode-ray tube envelope of the wide angle type which hasa rear cone section of rectangular truncated pyramidal shape.

SUMMARY OF THE INVENTION In a cathode-ray tube of this invention, theconical portion of a funnel-shaped tube envelope which includes tubularneck and conical portions comprises a rear cone section of rectangulartruncated pyramidal shape and a front cone flaring therefrom at a wideangle.

The cathode-ray tube envelope of this invention constructed as describedabove almost fully prevents the occurrence of neck shadows, enableselectron beams to be deflected at a wide angle and moreover permits theeasy fitting of the deflection coil at an accurate location.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of acathode-ray tube according to one embodiment of this invention;

FIG. 2 is a perspective view of a deflection coil;

FIG. 3 is a cross sectional view of a cathode-ray tube fitted with adeflection coil and convergence ring;

FIG. 4 is a cross sectional view of a cathode-ray tube according toanother embodiment of the invention with grooves formed along the insideof the ridges defined by the adjacent walls of a rear cone ofrectangular pyramidal shape;

FIG. 5 is a cross sectional view on line 5-5 of FIG. 4; and

FIG. 6 is a cross sectional view on line 6-6 of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1 to 3, afunnel-shaped glass envelope 11 a tubular neck bulb 12 integral with aconical portion 13 widely flaring from the front end of the neck bulb12. The front side of the envelope is sealed with a faceplate 14 havinga rectangular shape, the height of which bears a ratio of three-fourthsto the width and coated on the inner surface with a fluorescent screen15. This fluorescent screen 15 is an ordinary type used with a colorcathode-ray tube which is prepared by depositing fluorescent material onthe inside of the faceplate 14 in the form of dots constituting triadsor triplets, each representing three colors of red, green and blue, orin the form of extremely short strips collectively presenting adifferent pattern of arrangement in which they are juxtaposed in thespecified order of red, greenand blue. When excited by scanning electronbeams, the aforesaid dots or strips of fluorescent material glow red,green and blue. A shadow mask 16 is so disposed as to face the faceplate14 at a predetermined distance therefrom. In the neck bulb 12 isreceived a triple electron gun assembly 17 consisting of three electrongun members arranged in a triangular form or in a straight line.

According to the embodiment of FIGS. 1 to 3, the conical portion 13comprises a rear cone section 13a of rectangular truncated pyramidalshape which has a rectangular front end and a rear end integral with theneck bulb l2 and a front cone section 13b flaring from the rectangularfront end the rear cone section 13a at a wider angle which has arectangular large front end. The rear cone 13a should preferably have arectangular cross section similar to the rectangular form of thefaceplate 14 so as to resolve the problem of neck shadows.

To the rear end of the neck bulb 12 is attached a stem socket20'lengthwise penetrated by lead pins electrically connected to therespective electron gun members 18 of the electron gun assembly 17. Theelectron gun assembly is received in the neck bulb 12 with its top enddisposed adjacent to the front side of the neck bulb 12. There isprovided an electromagnetic deflection coil 21 so as to surround therear cone section 13a of the envelope l1. Said deflection coil 21 hasits interior formed into a rectangular truncated pyramidal shape similarto that of the rear cone 13a so as to ensure a close fit therewith and,as is well known, includes coil members for horizontal and verticaldeflection. Aroundpart of the neck bulb 12 is provided a convergenceadjusting means 22.

The shadow mask type color cathode-ray tube having the cathode ray tubeenvelope of the aforesaid construction is not fundamentally different inoperation from the ordinary type. Three beams of electrons emitted fromthe respective members of the triple electron gun assembly 17 have theirpassage deflected toward the'faceplate 14 by the deflection coil 21 tobe focused on the predetermined holes of the shadow mask, therebyexciting the corresponding points on the fluorescent screen 15 toreproduce color pictures on the faceplate 14.

According to the cahotde-ray tube envelope of this invention, the rearcone 13a is formed, as previously described, into a rectangulartruncated pyramidal shape, enabling electron beams from the electron gunassembly 17 to be deflected as widely as, for example, an angle of l andmore than 1 10 without being intercepted by the front part of the neckbulb 12, regardless of the direction of said deflection, so that theappearance of neck shadows at the screen corners is eliminated to permitreproduction of true shades of color even at said screen corners.

As mentioned above, the cathode-ray tube having the cathode ray tubeenvelope of this invention enables electron beams to be deflected at amuch wider angle than has been possible with the prior art type, thusprominently reducing the depth and weight of a color televisionreceiving set. Moreover, the rectangular truncated pyramidal shape ofthe interior of the deflection coil 21 similar to that of the rear cone13a permits an easy fitting therebetween. Further, insertion of a'tripleelectron gun assembly 17 into the neck bulb 12 in a conformity with thearrangement of the red, green and blue glowing dots or strips of thefluorescent screen can be effected more easily and accurately by takingone side of the rectangular cross section of the rear cone section 13aas a reference side, thereby enabling a cathode-ray tube to display anexcellent electrical performance.

There will now be described by reference to FIGS. 4 to 6 a modificationof the cathode-ray tube of this invention. According to saidmodification, the envelope 11 includes, as in the preceding embodiment,a conical portion 13 comprising a front cone section 13b and a rear conesection 13a of rectangular truncated pyramidal shape, and a neck bulb12. The difference between said modification and the foregoingembodiment is that there are formed four grooves 30 along the inside ofthe ridges defined by the adjacent walls of the rear cone section 130.These grooves 30 extend up to the corresponding corners of the rear sideof the front cone section 13b with a progressively increasing width andeach take a curved form at said comers, with the radius of curvature setat, for example, 2 mm at the front side of the rear cone section.

If the grooves 30 should be formed unduly deep, those parts of the wallsof the rear cone section 13a which are adjacent to said grooves 30 wouldbe cracked. To avoid such event, therefore, the grooves 30 shouldpreferably be formed to suchdepth that the aforesaid walls of the rearcone 13a retain at least half the original thickness. Formation of suchgrooves has the same effect as increasing the transversal dimension ofthe inner space of the rear cone 13a, thus contributing to minimize theoccurrence of neck shadows.

What we claim is:

LA cathode ray tube including an envelope comprising:

a tubular neck portion; and

a conical portion including:

a rear cone section of rectangular truncated pyramidal shape oversubstantially the whole length thereof, said rear cone section having arectangular front end and a rear end integral with said tubular neckportion, and four grooves extending along the inside of the ridgesdefined by the adjacent walls of said rear cone section, said groovesextending along substantially the length of said ridges and having aprogressively increasing width toward the scren end of the tube; and

a front cone section flaring from the rectangular front end of said rearcone section.

2. A cathode-ray tube according to claim 1 further comprising adeflection coil disposed around said rear cone section and having itsinterior formed into a rectangular truncated pyramidal shape similar tothat of the rear cone section so as to ensure a close fit therewith.

3. A cathode ray tube according to claim 1 further comprising afaceplate fixed to the rectangular wide end of said front cone section;a shadow mask interior of said envelope and facing said faceplate; and atriple electron gun assembly received in said neck portion.

4. A cathode ray tube according to claim 1 wherein at least the frontend of each of said grooves is curved.

5. A cathode ray tube envelope comprising: a tubular neck portion; and aconical portion including:

a rear cone section of rectangular truncated pyramidal shape oversubstantially the whole length thereof, said rear cone section having arectangular front end and a rear end integral with said tubular neckportion, and four grooves extending along the inside of the ridgesdefined by the adjacent walls of said rear cone section, said groovesextending along substantially the length of said ridges and having aprogressively increasing width toward the screen end of the tube; and

a front cone section flaring from the rectangular front end of said rearcone section. 6. A cathode ray tube according to claim 5 wherein atleast the front end of each of said grooves is curved.

1. A cathode ray tue including an envelope comprising: a tubular neckportion; and a conical portion including: a rear cone section ofrectangular truncated pyramidal shape over substantially the wholelength thereof, said rear cone section having a rectangular front endand a rear end integral with said tubular neck portion, and four groovesextending along the inside of the ridges defined by the adjacent wallsof said rear cone section, said grooves extending along substantiallythe length of said ridges and having a progressively increasing widthtoward the scren end of the tube; and a front cone section flaring fromthe rectangular front end of said rear cone section.
 2. A cathode-raytube according to claim 1 further comprising a deflection coil disposedaround said rear cone section and having its interior formed into arectangular truncated pyramidal shape similar to that of the rear conesection so as to ensure a close fit therewith.
 3. A cathode ray tubeaccording to claim 1 further comprising a faceplate fixed to therectangular wide end of said front cone section; a shadow mask interiorof said envelope and facing said faceplate; and a triple electron gunassembly received in said neck portion.
 4. A cathode ray tube accordingto claim 1 wherein at least the front end of each of said grooves iscurved.
 5. A cathode ray tube envelope comprising: a tubular neckportion; and a conical portion including: a rear cone section ofrectangular truncated pyramidal shape over substantially the wholelength thereof, said rear cone section having a rectangular front endand a rear end integral with said tubular neck portion, and four groovesextending along the inside of the ridges defined by the adjacent wallsof said rear cone section, said grooves extending along substantiallythe length of said ridges and having a progressively increasing widthtoward the screen end of the tube; and a front cone section flaring fromthe rectangular front end of said rear cone section.
 6. A cathode raytube according to claim 5 wherein at least the front end of each of saidgrooves is curved.